chore(release): bump version to 0.1.0-beta.3

[bihius]

Summary

• Bump backend, frontend, and log-shipper package versions to 0.1.0-beta.3
• Update release-kit references (.env.example, docker-compose.yml, README.md) to the new tag
• Add CHANGELOG entry summarizing changes since 0.1.0-beta.2 (banned-IPs admin UI, DDoS/auto-ban form UX, Apply-config reconciliation fix, banned-ips 502 fix)

Test plan

• uv run pytest --cov=app
• uv run mypy app/
• uv run ruff check app/
• pnpm run type-check
• pnpm run lint
• pnpm run test

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